An article here has a very nice downloadable map of human ventures out of Africa.It includes markers for areas where modern humans are thought to have intermingled with Neanderthals and Denisovans.Estimates of dates are included, as far back as 300ka.(I suppose our YEC friends would say that means 300,000 days ago.)It doesn't, however, say how the Neanderthals and Denisovans got there.http://science.sciencemag.org/content/358/6368/eaai9067The article is a long abstract, with a link to the whole paper behinds a paywall.